Polyamide Resin Integrally Molded Product, a Method for Manufacturing the Same, and a Joining Auxilary for Polyamide Resin

ABSTRACT

To provide a polyamide resin integrally molded product having high joining strength and excellent joining reliability, and a method for manufacturing the same, and also to provide a joining auxiliary capable of mutually joining polyamide resins with high joining strength. In manufacturing the polyamide resin integrally molded product by applying the joining auxiliary to a joint site of a polyamide resin molded product and welding a different polyamide resin which is to form an additive molded product part to the joint site, the joining auxiliary contains trihydroxybenzene and/or trihydroxybenzoic acid as a component (A) and an organic solvent which is capable of dissolving or dispersing the component (A) as a component (B). At this time, it is preferable for the component (A) to further contain dihydroxybenzene and/or dihydroxybenzoic acid.

TECHNICAL FIELD

The present invention relates to a polyamide resin integrally moldedproduct, a method for manufacturing the same, and a joining auxiliarysuitably used for joining polyamide resins.

BACKGROUND ART

A linear polymer having amide bonds as a repeating unit within themolecules is generally called a polyamide resin. Among polyamide resins,a resin mainly having aliphatic chains is in widespread use as “Nylon”(commercial name), typically including Nylon 6, Nylon 66 and the like.

The polyamide resin is a crystalline polymer in which hydrogen bonds canbe formed between amide bonds of different polymer chains, and has arobust crystalline structure which is comprised of planes arranged inlayers while the amide bonds are regularly hydrogen-bonded with eachother within one plane.

Owing to polarity and the crystalline structure brought by such amidebonds, the polyamide resin has excellent resistance to ahydrocarbon-based solvent such as gasoline and oil, and relatively highheat resistance and strength; therefore, the polyamide resin is inwidespread use as a resin material suitable for automotive parts,machine parts and the like.

In recent years, the automotive parts and the like have been gettingmore complicated in shape and larger in size, so that it has becomedifficult to obtain a polyamide resin integrally molded product having adesired shape by single injection molding, extrusion molding or thelike. Therefore, an attempt is made to separately mold plural polyamideresin molded products, and mutually join the products to integrate intoa polyamide resin integrally molded product of a desired shape.

For example, Japanese Patent Application Laid-Open No. 2000-61983discloses a polyamide resin integrally molded product which is obtainedby injection-molding a polyamide resin as a secondary molding materialon a primary molded product consisting of a polyamide resin to mutuallyweld and integrate the primary molded product and an additive moldedpart made of the secondary molding material.

It is also known to manufacture a polyamide resin integrally moldedproduct by mutually welding and integrating polyamide resin moldedproducts by use of a welding method such as ultrasonic welding andvibration welding.

Further, it is also known to manufacture a polyamide resin integrallymolded product by use of a resistance welding method by which apolyamide resin being a secondary molding material is injection-moldedwhile a primary molded product consisting of a polyamide resin is meltedby heating a conductive wire buried in the primary molded product, andthe primary molded product and the additive molded product part aremutually welded.

However, conventionally known polyamide resin integrally molded productshave a problem such as poor reliability and the like, resulting frominsufficient joining strength. This is assumed to be attributable to thefollowing reasons.

When a polyamide resin integrally molded product is manufactured bymeans of injection molding, a primary molded product consisting of apolyamide resin is set in a mold, and a melted polyamide resin which isto form an additive molded product part is injection-molded on theprimary molded product.

It is considered that free amide bonds which do not take part inhydrogen bonding are present in a joint site of the primary moldedproduct because polymer chains to be hydrogen-bonded therewith aregenerally absent.

However, the free amide bonds are unintentionally mutually bonded by theapplication of heat to the mold in injection molding or the like,causing association to the joint site surface of the primary moldedproduct. Therefore, it is assumed that the free amide bonds are reducedsignificantly in the joint site surface of the primary molded product.

Accordingly, while the amide bonds on the primary molded product sideand the amide bonds on the additive molded product side are nothydrogen-bonded, the primary molded product and the additive moldedproduct are independently crystallized, and thereby the joining strengthof the resulting integrated molded product is reduced considerably.

In addition to the above, the polyamide resin has an extremely narrowmelting point width and an extremely short hardening time, compared withother resins. Therefore, this is also conceivably responsible for theinsufficient joining of the primary molded product to the additivemolded product.

The problem of the reduction in joining strength as described above canoccur also in the case of manufacturing a polyamide resin integrallymolded product by use of a welding method such as ultrasonic welding andvibration welding.

More specifically, when a polyamide resin integrally molded product ismanufactured by ultrasonic welding or vibration welding, not only thejoint site surfaces but also the whole joint sites are generally neededto be joined while being heated and melted by vibrational energy forensuring sufficient joining strength.

However, joining of once-crystallized molded products needs applicationof enormous vibrational energy, so that a remelt and resolidified layerinferior in strength is remarkably produced in the joint sites.

Accordingly, it is difficult to obtain an integrally molded producthaving sufficient joining strength by simply using the conventionalultrasonic welding, vibration welding or the like. In addition, there isanother problem that the joint sites have to be designed to be thickerthan essentially required to ensure sufficient joining strength.

In addition, in the manufacture of a polyamide resin integrally moldedproduct by resistance welding, the conductive wire must be buried in theprimary molded product, leading to extremely poor work efficiency and anincreased manufacturing cost. It is also assumed that the strength isreduced since a remelt and resolidified layer inferior in strength isproduced by the heat generation of the conductive wire on the primarymolded product side. Further, inclusion of the conductive wire in theintegrally molded product is not preferred from the viewpoint ofrecycling.

From the point of the above-mentioned problems, the present inventionthus provides a polyamide resin integrally molded product having highjoining strength and excellent joining reliability, and a method formanufacturing the same. The present invention further provides a joiningauxiliary capable of mutually joining polyamide resins with high joiningstrength.

DISCLOSURE OF THE INVENTION

To achieve the objects and in accordance with the purpose of the presentinvention, a polyamide resin integrally molded product described inclaim 1 includes a polyamide resin molded product to a joint site ofwhich a joining auxiliary is applied, and a polyamide resin to form anadditive molded product part which is welded to the joint site of thepolyamide resin molded product to be integrated, where the joiningauxiliary contains trihydroxybenzene and/or trihydroxybenzoic acid as acomponent (A) and an organic solvent which is capable of dissolving ordispersing the component (A) as a component (B).

In addition, a polyamide resin integrally molded product described inclaim 2 includes a polyamide resin molded product and another polyamideresin molded product, to at least one joint site of the polyamide resinmolded products, a joining auxiliary being applied to mutually weld andintegrate the joint sites, where the joining auxiliary containstrihydroxybenzene and/or trihydroxybenzoic acid as a component (A) andan organic solvent which is capable of dissolving or dispersing thecomponent (A) as a component (B).

A polyamide resin integrally molded product described in claim 3 is thepolyamide resin integrally molded product according to claim 1 or 2,where the component (A) further contains dihydroxybenzene and/ordihydroxybenzoic acid.

A polyamide resin integrally molded product described in claim 4 is thepolyamide resin integrally molded product according to any one of claims1 to 3, where a content of the component (A) is not less than 1 wt % andnot more than 50 wt %, and a content of the component (B) is not lessthan 50 wt % and not more than 99 wt %.

A polyamide resin integrally molded product described in claim 5 is thepolyamide resin integrally molded product according to any one of claims1 to 4, where the component (B) is a mixed organic solvent obtained bymixing two or more sorts of the organic solvents.

In addition, a method for manufacturing a polyamide resin integrallymolded product described in claim 6 includes the steps of applying ajoining auxiliary to a joint site of a polyamide resin molded product,and welding a polyamide resin which is to form an additive moldedproduct part to the joint site of the polyamide resin molded product,where the joining auxiliary contains trihydroxybenzene and/ortrihydroxybenzoic acid as a component (A) and an organic solvent whichis capable of dissolving or dispersing the component (A) as a component(B).

In addition, a method for manufacturing a polyamide resin integrallymolded product described in claim 7 includes the steps of applying ajoining auxiliary to at least one joint site of polyamide resin moldedproducts, and welding the joint sites mutually, where the joiningauxiliary contains trihydroxybenzene and/or trihydroxybenzoic acid as acomponent (A) and an organic solvent which is capable of dissolving ordispersing the component (A) as a component (B).

A method for manufacturing the polyamide resin integrally molded productdescribed in claim 8 is the method for manufacturing the polyamide resinintegrally molded product according to claim 6 or 7, where the component(A) further contains dihydroxybenzene and/or dihydroxybenzoic acid. Amethod for manufacturing the polyamide resin integrally molded productdescribed in claim 9 is the method for manufacturing the polyamide resinintegrally molded product according to any one of claims 6 to 8, where acontent of the component (A) is not less than 1 wt % and not more than50 wt %, and a content of the component (B) is not less than 50 wt % andnot more than 99 wt %.

A method for manufacturing the polyamide resin integrally molded productdescribed in claim 10 is the method for manufacturing the polyamideresin integrally molded product according to any one of claims 6 to 9,where the component (B) is a mixed organic solvent obtained by mixingtwo or more sorts of the organic solvents.

In addition, a joining auxiliary for polyamide resin described in claim11 contains trihydroxybenzene and/or trihydroxybenzoic acid as acomponent (A) and an organic solvent which is capable of dissolving ordispersing the component (A) as a component (B).

A joining auxiliary for polyamide resin described in claim 12 is thejoining auxiliary for polyamide resin according to claim 11, where thecomponent (A) further contains dihydroxybenzene and/or dihydroxybenzoicacid.

A joining auxiliary for polyamide resin described in claim 13 is thejoining auxiliary for polyamide resin according to claim 11 or 12, wherea content of the component (A) is not less than 1 wt % and not more than50 wt %, and a content of the component (B) is not less than 50 wt % andnot more than 99 wt %.

A joining auxiliary for polyamide resin described in claim 14 is thejoining auxiliary for polyamide resin according to any one of claims 11to 13, where the component (B) is a mixed organic solvent obtained bymixing two or more sorts of the organic solvents.

The polyamide resin integrally molded product according to the presentinvention is obtained by welding the different polyamide resin which isto form the additive molded product part to the joint site of thepolyamide resin molded product to integrate, the joint sitesurface-modified by the joining auxiliary, or by mutually welding thejoint site of the polyamide resin molded product and the joint site ofthe different polyamide resin molded product to integrate, one or bothof the joint sites surface-modified by the joining auxiliary.

As the joining auxiliary, used is the joining auxiliary containing thetrihydroxybenzene and/or trihydroxybenzoic acid as the component (A) andthe organic solvent which is capable of dissolving or dispersing thecomponent (A) as the component (B).

Owning to this, high joining strength and excellent joining reliabilitycan be ensured. In addition, high joining strength can be ensuredwithout providing a so-called joining margin by thickening the jointsite or the like.

When the joining auxiliary further contains the dihydroxybenzene and/ordihydroxybenzoic acid as the component (A), improvement in joiningstrength of the polyamide integrally molded product can be expected.

In addition, since the component (A) is rich in compounds having asurface modifying effect, there is an advantage of facilitating riskdistribution for the compounds. There is also another advantage ofincreasing flexibility in adjusting the composition of the joiningauxiliary so as to reduce a cost thereof in response to pricefluctuation of the compounds.

When the content of the component (A) is within the range from not lessthan 1 wt % to not more than 50 wt %, and the content of the component(B) is within the range from not less than 50 wt % to not more than 99wt %, the above-mentioned advantages can be further ensured.

When the mixed organic solvent obtained by mixing two or more sorts ofthe organic solvents capable of dissolving or dispersing the component(A) is used as the component (B) of the joining auxiliary, drying timeby vaporization or the like of the joining auxiliary is easy to adjustand the joining auxiliary are excellent in coating properties comparedwith a case of using the organic solvent by one sort. Consequently, thejoining auxiliary is uniformly applied to the joint site tosurface-modify evenly, ensuring particularly excellent joiningreliability.

The method for manufacturing the polyamide resin integrally moldedproduct according to the present invention includes the steps ofapplying the joining auxiliary to the joint site of the polyamide resinmolded product and welding the polyamide resin which is to form theadditive molded product part to the joint site, or includes the steps ofapplying the joining auxiliary to the joint site of the polyamide resinmolded product and/or the joint site of the different polyamide resinmolded product and mutually welding the joint sites.

As the above-mentioned joining auxiliary, used is the joining auxiliarycontaining the trihydroxybenzene and/or trihydroxybenzoic acid as thecomponent (A) and the organic solvent capable of dissolving ordispersing the component (A) as the component (B).

Therefore, a polyamide resin integrally molded product having highjoining strength and excellent joining reliability can be obtained.Compared with a conventional manufacturing method, the polyamideresin-integrally molded product can be easily manufactured at low cost.

When the joining auxiliary further contains the dihydroxybenzene and/ordihydroxybenzoic acid as the component (A), improvement in joiningstrength of the resulting polyamide resin integrally molded product canbe expected.

In addition, since the component (A) is rich in compounds having asurface modifying effect, there is an advantage of facilitating riskdistribution for the compounds. There is also another advantage ofincreasing flexibility in adjusting the composition of the joiningauxiliary so as to reduce a cost thereof in response to pricefluctuation of the compounds.

When the content of the component (A) is within the range from not lessthan 1 wt % to not more than 50 wt %, and the content of the component(B) is within the range from not less than 50 wt % to not more than 99wt %, the above-mentioned advantages can be further ensured.

When the mixed organic solvent obtained by mixing two or more sorts ofthe organic solvents capable of dissolving or dispersing the component(A) is used as the component (B) of the joining auxiliary, drying timeby vaporization or the like of the joining auxiliary is easy to adjustand the joining auxiliary are excellent in coating properties comparedwith a case of using the organic solvent by one sort. Consequently, thejoining auxiliary can be uniformly applied to the joint site tosurface-modify evenly, ensuring particularly excellent joiningreliability.

The joining auxiliary for polyamide resin according to the presentinvention can mutually join polyamide resins with high joining strengthsince it contains the trihydroxybenzene and/or trihydroxybenzoic acid asthe component (A) and the organic solvent which is capable of dissolvingor dispersing the component (A) as the component (B).

When the joining auxiliary further contains the dihydroxybenzene and/ordihydroxybenzoic acid as the component (A), improvement in joiningstrength in mutually joining polyamide resins can be expected.

In addition, since the component (A) is rich in compounds having asurface modifying effect, there is an advantage of facilitating riskdistribution for the compounds. There is also another advantage ofincreasing flexibility in adjusting the composition of the joiningauxiliary so as to reduce a cost thereof in response to pricefluctuation of the compounds.

When the content of the component (A) is within the range from not lessthan 1 wt % to not more than 50 wt %, and the content of the component(B) is within the range from not less than 50 wt % to not more than 99wt %, the above-mentioned advantages can be further ensured.

When the mixed organic solvent obtained by mixing two or more sorts ofthe organic solvents capable of dissolving or dispersing the component(A) is used as the component (B) of the joining auxiliary, drying timeby vaporization or the like of the joining auxiliary is easy to adjustand the joining auxiliary are excellent in coating properties comparedwith a case of using the organic solvent by one sort. Consequently, thejoining auxiliary can be uniformly applied to the joint site tosurface-modify evenly.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are external perspective views respectively showing atest piece P and a primary molded part P1 constituting it, which areconsistent with the embodiment of the present invention.

FIG. 2 is an external perspective view showing a mold used for moldingthe test piece P consistent with the embodiment of the present inventionby injection molding.

BEST MODE FOR CARRYING OUT THE INVENTION

A preferred embodiment of the present invention will be furtherdescribed in detail.

A polyamide resin integrally molded product according to the presentinvention (hereinafter referred to as the “present polyamide resinintegrally molded product”) is obtained by applying a joining auxiliaryaccording to the present invention (hereinafter referred to as the“present joining auxiliary”) to a joint site of a polyamide resin moldedproduct, and welding a different polyamide resin that is to form anadditive molded product part to this joint site, or by applying thepresent joining auxiliary to a joint site of a polyamide resin moldedproduct and/or a joint site of a different polyamide resin moldedproduct, and mutually welding these joint sites.

As the present polyamide resin integrally molded product which isobtained by the former manner, specifically cited is an integrallymolded product which can be obtained by applying the present joiningauxiliary to a joint site of a polyamide resin molded product, insertingthe molded product into a mold, newly injecting a melted polyamide resinthereinto, and welding the additive molded product part to the polyamideresin molded product.

On the other hand, as the present polyamide resin integrally moldedproduct which is obtained by the latter manner, specifically cited is anintegrally molded product which can be obtained by applying the presentjoining auxiliary to a joint site of a polyamide resin molded productand/or a joint site of a different polyamide resin molded product, andmutually welding the joint sites by various welding methods associatedwith heat melting of a resin such as ultrasonic welding, vibrationwelding, hot plate welding, hot air welding, high frequency welding,spin welding, friction welding, laser welding, electromagnetic inductionwelding, and infrared welding.

As the above-described polyamide resin, specifically named are aliphaticpolyamides such as Nylon 6, Nylon 66, Nylon MX6, Nylon 11, Nylon 12,Nylon 46, Nylon 610 and Nylon 612, aromatic polyamides, and the like,which may be employed by one sort, or more than one sort in combination.Polymer alloy-based resins containing such polyamide resins can also beused.

Besides, the polyamide resin integrally molded product and the polyamideresin molded product may take various shapes such as a hollow shape,which can be selected as appropriate according to the purpose of use.

In addition, the polyamide resin molded product may be obtained byinjection molding, blow molding, extrusion molding, transfer molding,compression molding, cutting work or the like. The polyamide resinmolded product may have plural joint sites, which is not limited inparticular.

Hereinafter, the present joining auxiliary used in the manufacture ofthe present polyamide resin integrally molded product will be described.

The present joining auxiliary contains trihydroxybenzene and/ortrihydroxybenzoic acid as a component (A) and an organic solvent whichis capable of dissolving or dispersing the component (A) as a component(B).

For the trihydroxybenzene in the component (A) , named are1,2,3-trihydroxybenzene (CAS No. RN [87-66-1], pyrogallol),1,2,4-trihydroxybenzene (CAS No. RN [533-73-3]), 1,3,5-trihydroxybenzene(CAS No. RN [108-73-6]), and 1,3,5-trihydroxybenzene dehydrate (CAS No.RN [6099-90-7]).

In addition, for the trihydroxybenzoic acid, named are2,3,4-trihydroxybenzoic acid (CAS No. RN [610-02-6]),2,4,6-trihydroxybenzoic acid (CAS No. RN [83-30-79]),2,4,6-trihydroxybenzoic acid monohydrate (CAS NO. RN [71989-93-0]),3,4,5-trihydroxybenzoic acid (CAS No. RN [149-91-7], gallic acid), and3,4,5-trihydroxybenzoic acid monohydrate (CAS No. RN [5995-86-8]).

The present joining auxiliary may further contain dihydroxybenzeneand/or dihydroxybenzoic acid. This is because joining strength of thepolyamide resin integrally molded product tends to be improved as thecontent of the component (A) is increased.

In addition, if the component (A) is rich in such compounds that have asurface modifying effect, there is also an advantage of facilitatingrisk dispersion for the compounds. There is also another advantage ofadjusting the composition of the joining auxiliary so as to reduce acost thereof in response to price fluctuation of the compounds.

For the dihydroxybenzene, named are 1,2-dihydroxybenzene (CAS No. RN[120-80-9]), 1,3-dihydroxybenzene (CAS No. [108-46-3]), and1,4-dihydroxybenzene (CAS No. RN [123-31-9]).

For the dihydroxybenzoic acid, named are 2,3-dihydroxybenzoic acid (CASNo. RN [303-38-8]), 2,4-dihydroxybenzoic acid (CAS No. RN [89-86-1]),2,5-dihydroxybenzoic acid (CAS No. RN [490-79-9]), 2,6-dihydroxybenzoicacid (CAS No. RN [303-07-1]), 3,4-dihydroxybenzoic acid (CAS No. RN[99-50-3]), and 3,5-dihydroxybenzoic acid (CAS No. RN [99-10-5]).

Meanwhile, as the organic solvent, either volatile one or nonvolatileone may be used while the volatile one is preferably used. Additionally,organic solvents capable of slightly dissolving a polyamide resin can besuitably used.

For the organic solvent, specifically named are alcohols having 1 to 6carbon atoms, ketones or aldehydes having 1 to 6 carbon atoms, andnitrites having 1 to 6 carbon atoms, and more specifically named aremethanol, ethanol, isopropyl alcohol, acetone, acetonitrile and thelike, which may be employed by one sort, or more than one sort incombination.

At this time, when more than one sort of organic solvents are mixed andused as a mixed organic solvent, there is an advantage of enabling thedrying time to be adjusted as appropriate so that the present joiningauxiliary is not immediately dried after applied to the joint site,taking into consideration the ambient temperature and the workingenvironment in which the present joining auxiliary is used.

As the mixing ratio of the component (A) to the component (B), it ispreferable that the content of the component (A) is within the rangefrom not less than 1 wt % to not more than 50 wt %, and the content ofthe component (B) is within the range from not less than 50 wt % to notmore than 99 wt %, from the viewpoint of providing high joining strengthand the like.

More preferably, the content of the component (A) is within the rangefrom not less than 5 wt % to not more than 25 wt %, and the content ofthe component (B) is within the range from not less than 75 wt % to notmore than 95 wt %, and still more preferably, the content of thecomponent (A) is within the range from not less than 5 wt % to not morethan 15 wt %, and the content of the component (B) within the range fromnot less than 85 wt % to not more than 95 wt %.

At this time, it is not preferable for the content of the component (A)to exceed 50 wt % and for the content of the component (B) to fall below50 wt % since it tends to be difficult for the component (A) to bedissolved in the component (B).

Meanwhile, it is not preferable for the content of the component (A) tofall below 1 wt % and for the content of the component (B) to exceed 99wt % since the joining strength of the polyamide resin integrally moldedproduct tends to be reduced.

In addition, the present joining auxiliary may be manufactured by anymanufacturing method by which the component (A) can be uniformlydissolved or dispersed in the component (B), which is not limited inparticular.

Besides, the above-mentioned polyamide resin, a dye, a thickener, anantioxidant and the like may be added to the present joining auxiliaryto an extent such that a surface modifying effect on the polyamide resinis not impaired.

For example, in the case of adding the polyamide resin, joiningreliability can be increased. This is assumed because asperities on thejoint site surface are reduced by a contact area increased by the addedpolyamide resin.

At this time, as the polyamide resin to be added, a polyamide resin ofthe same type as the molded product to be joined to is preferably used.

In addition, for example, in the case of adding a dye, an applicationstate of the join site can be visually checked, allowing applicationworkability to improve to decrease unevenness in application.

In addition, for example, in the case of adding a thickener, an effectsuch as dropping prevention, uniform coating and the like can be gainedin applying the joining auxiliary.

As an application manner of the present joining auxiliary to the jointsite, it is essential only that the present joining auxiliary can bethinly spread and applied by a fixed quantity to the joint site, whichis not limited in particular hereto. Specifically, various applicationmethods such as application by brush and application by sponge can beemployed.

Here, the reason why the present polyamide resin integrally moldedproduct has high joining strength is assumed as follows.

When the present joining auxiliary is applied to the joint site of thepolyamide resin molded product, the polyamide resin in the joint sitesurface is activated by a reduction effect of the component (A). Then,when the melted polyamide resin is provided to the activated joint site,or the joint sites are mutually welded, both of the joint sites arestrongly connected to be integrated mainly by chemical bonding in arecrystallizing process of the melted polyamide resin.

Therefore, the resulting polyamide resin integrally molded product hashigh joining strength bearing comparison to a molded product which isintegrally molded at a time.

EXAMPLES

Hereinafter, the present invention will be described more specificallyreferring to Examples.

[Preparation of Joining Auxiliaries Consistent with the PresentExamples]

Firstly, joining auxiliaries consistent with the present Examples wereprepared according to the following procedure. As shown in Tables 1 to15 described below, the joining auxiliaries consistent with the presentExamples were prepared by blending 1,2,3-trihydroxybenzene (pyrogallol),3,4,5-trihydroxybenzoic acid (gallic acid), 1,3-dihydroxybenzene, and3,5-dihydroxybenzoic acid as the component (A) with methanol andisopropyl alcohol as the component (B) so as to have predeterminedweight ratios followed by sufficient mixing by use of a stirrer.

Besides, the joining auxiliaries of Examples 35 to 68 in the tables havethe same compositions as the joining auxiliaries of Examples 1 to 34.

1,2,3-trihydroxybenzene, 3,4,5-trihydroxybenzoic acid,1,3-dihydroxybenzene, 3,5-dihydroxybenzoic acid, methanol and isopropylalcohol used therein were manufactured by Wako Pure Chemical Industries.

(Preparation of Test Pieces Consistent with Present Examples)

FIGS. 1A and 1B are external perspective views respectively showing atest piece P and a primary molded part P1 constituting it. FIG. 2 is anexternal perspective view showing a mold used for molding the test pieceP by injection molding.

The test pieces P consisting of a polyamide resin were produced byinjection molding according to the following procedure: the presentjoining auxiliaries consistent with the present Examples were applieduniformly by use of a brush to joint end surfaces 1 of the primarymolded parts P1 preliminarily molded by injection molding, and themolded parts were set in dies 2 and 3, and then additive molded parts P2were added thereto by injection, whereby the test pieces P consistentwith the present Examples in which the primary molded parts P1 and theadditive molded parts P2 were welded to be integrated were produced.

The test pieces P were molded in a rectangular shape with a uniformthickness. The primary molded parts P1 and the additive molded parts P2have the same shape (Length:L×Width:W×Thickness:T=40×10×3 mm), and thetest pieces P formed by mutually joining both the parts have a totallength of 80 mm.

As a material for the test pieces P, Nylon 6 resin (manufactured byToray Industries, “AMILAN CM 1026”), Nylon 66 resin (manufactured by DuPont, “ZYTEL 101L”), or Nylon 12 resin (manufactured by Daicel-Degussa,“DAIAMID L1640”) was used.

Conditions of injection molding were set as follows. As an injectionmolding device, “SE-18S” manufactured by Sumitomo Heavy Industries wasused. The molding temperatures were set to 240-245-240-235° C. in orderfrom the injection nozzle for Nylon 6, 290-295-290-285° C. in order fromthe injection nozzle for Nylon 66, and 230-235-230-225° C. in order fromthe injection nozzle for Nylon 12.

The molding temperatures were set to 65° C. in molding the primarymolded part P1 and 95° C. in molding the secondary molded part P2 forNylon 6 and Nylon 66. The temperatures were set to 50° C. in moldingboth the primary molded part P1 and the secondary molded part P2 forNylon 12.

(Evaluation of Test Pieces Consistent with Present Examples)

The test pieces P were evaluated as follows: the test pieces P weresubjected to a tension test in a thermostatic chamber at a roomtemperature of 23° C. and a humidity of 50% to measure the maximumtensile strengths at which the test pieces P were fractured (samplenumber: N=5). At this time, the test rate was set to 5 mm/min. As atension testing machine, a universal material testing machine (INSTRON4505) was used.

(Test Results of Joining Auxiliaries and Test Pieces Consistent withPresent Examples)

The test results of the joining auxiliaries and the 5 test piecesconsistent with the present Examples are shown in Tables 1 to 15.

Besides, the test pieces of Examples 1 to 34 consist of Nylon 6 resin,the test pieces of Examples 35 to 68 consist of Nylon 66 resin, and thetest pieces of Examples 69 to 71 consist of Nylon 12 resin. TABLE 1Example 1 Example 2 Example 3 Example 4 Example 51,2,3-trihydroxybenzene (wt %) 4.0 8.0 12.0 16.0 20.03,4,5-trihydroxybenzoic Acid (wt %) 1,3-dihydroxybenzene (wt %)3,5-dihydroxybenzoic Acid (wt %) Methanol (wt %) 48.0 46.0 44.0 42.040.0 Isopropyl Alcohol (wt %) 48.0 46.0 44.0 42.0 40.0 Tensile Strength(MPa) 46.5 49.4 58.5 60.8 54.3 Standard Deviation (MPa) 5.9 8.2 9.3 9.17.4

TABLE 2 Example 6 Example 7 Example 8 Example 9 Example 101,2,3-trihydroxybenzene (wt %) 24.0 28.0 3,4,5-trihydroxybenzoic Acid(wt %) 4.0 8.0 12.0 1,3-dihydroxybenzene (wt %) 3,5-dihydroxybenzoicAcid (wt %) Methanol (wt %) 38.0 36.0 48.0 46.0 44.0 Isopropyl Alcohol(wt %) 38.0 36.0 48.0 46.0 44.0 Tensile Strength (MPa) 48.2 44.6 53.251.9 56.5 Standard Deviation (MPa) 4.4 6.8 8.3 5.9 7.2

TABLE 3 Example 11 Example 12 Example 13 Example 14 Example 151,2,3-trihydroxybenzene (wt %) 4.0 3,4,5-trihydroxybenzoic Acid (wt %)16.0 20.0 24.0 28.0 4.0 1,3-dihydroxybenzene (wt %) 3,5-dihydroxybenzoicAcid (wt %) Methanol (wt %) 42.0 40.0 38.0 36.0 46.0 Isopropyl Alcohol(wt %) 42.0 40.0 38.0 36.0 46.0 Tensile Strength (MPa) 58.3 61.2 53.856.2 49.3 Standard Deviation (MPa) 6.1 5.5 6.8 4.5 6.5

TABLE 4 Example 16 Example 17 Example 18 Example 19 Example 201,2,3-trihydroxybenzene (wt %) 8.0 12.0 8.0 12.0 16.03,4,5-trihydroxybenzoic Acid (wt %) 8.0 12.0 1,3-dihydroxybenzene (wt %)4.0 8.0 8.0 3,5-dihydroxybenzoic Acid (wt %) Methanol (wt %) 42.0 38.044.0 40.0 38.0 Isopropyl Alcohol (wt %) 42.0 38.0 44.0 40.0 38.0 TensileStrength (MPa) 64.5 62.4 57.1 65.9 53.5 Standard Deviation (MPa) 8.3 9.06.2 10.1 3.9

TABLE 5 Example 21 Example 22 Example 23 Example 24 Example 251,2,3-trihydroxybenzene (wt %) 8.0 12.0 3,4,5-trihydroxybenzoic Acid (wt%) 8.0 12.0 16.0 1,3-dihydroxybenzene (wt %) 4.0 8.0 8.03,5-dihydroxybenzoic Acid (wt %) 4.0 8.0 Methanol (wt %) 44.0 40.0 38.044.0 40.0 Isopropyl Alcohol (wt %) 44.0 40.0 38.0 44.0 40.0 TensileStrength (MPa) 63.0 58.1 55.5 58.5 63.9 Standard Deviation (MPa) 7.1 8.97.3 9.1 6.2

TABLE 6 Example 26 Example 27 Example 28 Example 29 Example 301,2,3-trihydroxybenzene (wt %) 16.0 6.0 3,4,5-trihydroxybenzoic Acid (wt%) 8.0 12.0 16.0 6.0 1,3-dihydroxybenzene (wt %) 4.03,5-dihydroxybenzoic Acid (wt %) 8.0 4.0 8.0 8.0 Methanol (wt %) 38.044.0 40.0 38.0 42.0 Isopropyl Alcohol (wt %) 38.0 44.0 40.0 38.0 42.0Tensile Strength (MPa) 65.7 59.5 49.6 66.0 62.1 Standard Deviation (MPa)7.3 10.2 8.3 7.9 15.1

TABLE 7 Example 31 Example 32 Example 33 Example 341,2,3-trihydroxybenzene (wt %) 6.0 8.0 4.0 3,4,5-trihydroxybenzoic Acid(wt %) 6.0 8.0 4.0 1,3-dihydroxybenzene (wt %) 4.0 4.0 4.03,5-dihydroxybenzoic Acid (wt %) 4.0 4.0 4.0 4.0 Methanol (wt %) 42.042.0 42.0 42.0 Isopropyl Alcohol (wt %) 42.0 42.0 42.0 42.0 TensileStrength (MPa) 69.8 66.9 60.1 64.6 Standard Deviation (MPa) 6.9 8.2 9.34.2

TABLE 8 Example 35 Example 36 Example 37 Example 38 Example 391,2,3-trihydroxybenzene (wt %) 4.0 8.0 12.0 16.0 20.03,4,5-trihydroxybenzoic Acid (wt %) 1,3-dihydroxybenzene (wt %)3,5-dihydroxybenzoic Acid (wt %) Methanol (wt %) 48.0 46.0 44.0 42.040.0 Isopropyl Alcohol (wt %) 48.0 46.0 44.0 42.0 40.0 Tensile Strength(MPa) 52.6 70.9 72.3 68.5 63.2 Standard Deviation (MPa) 5.8 9.1 4.5 6.33.9

TABLE 9 Example 40 Example 41 Example 42 Example 43 Example 441,2,3-trihydroxybenzene (wt %) 24.0 28.0 3,4,5-trihydroxybenzoic Acid(wt %) 4.0 8.0 12.0 1,3-dihydroxybenzene (wt %) 3,5-dihydroxybenzoicAcid (wt %) Methanol (wt %) 38.0 36.0 48.0 46.0 44.0 Isopropyl Alcohol(wt %) 38.0 36.0 48.0 46.0 44.0 Tensile Strength (MPa) 59.8 58.2 62.360.4 58.4 Standard Deviation (MPa) 10.6 11.2 5.0 5.8 9.2

TABLE 10 Example 45 Example 46 Example 47 Example 48 Example 491,2,3-trihydroxybenzene (wt %) 4.0 3,4,5-trihydroxybenzoic Acid (wt %)16.0 20.0 24.0 28.0 4.0 1,3-dihydroxybenzene (wt %) 3,5-dihydroxybenzoicAcid (wt %) Methanol (wt %) 42.0 40.0 38.0 36.0 46.0 Isopropyl Alcohol(wt %) 42.0 40.0 38.0 36.0 46.0 Tensile Strength (MPa) 66.9 59.0 61.364.5 66.2 Standard Deviation (MPa) 8.9 9.9 9.5 10.5 5.6

TABLE 11 Example 50 Example 51 Example 52 Example 53 Example 541,2,3-trihydroxybenzene (wt %) 8.0 12.0 8.0 12.0 16.03,4,5-trihydroxybenzoic Acid (wt %) 8.0 12.0 1,3-dihydroxybenzene (wt %)4.0 8.0 8.0 3,5-dihydroxybenzoic Acid (wt %) Methanol (wt %) 42.0 38.044.0 40.0 38.0 Isopropyl Alcohol (wt %) 42.0 38.0 44.0 40.0 38.0 TensileStrength (MPa) 63.2 67.8 64.5 69.6 60.5 Standard Deviation (MPa) 6.3 9.47.3 8.6 4.8

TABLE 12 Example 55 Example 56 Example 57 Example 58 Example 591,2,3-trihydroxybenzene (wt %) 8.0 12.0 3,4,5-trihydroxybenzoic Acid (wt%) 8.0 12.0 16.0 1,3-dihydroxybenzene (wt %) 4.0 8.0 8.03,5-dihydroxybenzoic Acid (wt %) 4.0 8.0 Methanol (wt %) 44.0 40.0 38.044.0 40.0 Isopropyl Alcohol (wt %) 44.0 40.0 38.0 44.0 40.0 TensileStrength (MPa) 61.1 64.4 67.7 61.9 64.8 Standard Deviation (MPa) 10.312.2 8.2 8.5 4.3

TABLE 13 Example 60 Example 61 Example 62 Example 63 Example 641,2,3-trihydroxybenzene (wt %) 16.0 6.0 3,4,5-trihydroxybenzoic Acid (wt%) 8.0 12.0 16.0 6.0 1,3-dihydroxybenzene (wt %) 4.03,5-dihydroxybenzoic Acid (wt %) 8.0 4.0 8.0 8.0 Methanol (wt %) 38.044.0 40.0 38.0 42.0 Isopropyl Alcohol (wt %) 38.0 44.0 40.0 38.0 42.0Tensile Strength (MPa) 58.7 69.9 71.0 68.2 69.5 Standard Deviation (MPa)6.1 6.3 4.3 4.8 10.5

TABLE 14 Example 65 Example 66 Example 67 Example 681,2,3-trihydroxybenzene (wt %) 6.0 8.0 4.0 3,4,5-trihydroxybenzoic Acid(wt %) 6.0 8.0 4.0 1,3-dihydroxybenzene (wt %) 4.0 4.0 4.03,5-dihydroxybenzoic Acid (wt %) 4.0 4.0 4.0 4.0 Methanol (wt %) 42.042.0 42.0 42.0 Isopropyl Alcohol (wt %) 42.0 42.0 42.0 42.0 TensileStrength (MPa) 72.6 70.8 71.9 66.3 Standard Deviation (MPa) 5.4 8.2 9.99.6

TABLE 15 Example Example Example 69 70 71 1,2,3-trihydroxybenzene (wt %)8.0 2.0 3,4,5-trihydroxybenzoic (wt %) 8.0 8.0 Acid 1,3-dihydroxybenzene(wt %) 8.0 6.0 3,5-dihydroxybenzoic Acid (wt %) 8.0 Methanol (wt %) 42.042.0 42.0 Isopropyl Alcohol (wt %) 42.0 42.0 42.0 Tensile Strength (MPa)37.2 40.8 29.9 Standard Deviation (MPa) 3.6 1.8 9.3(Test Results of Test Pieces Consistent with Present Examples)

Test pieces consistent with Comparative Examples 1 to 6 will bedescribed first.

Comparative Example 1

A test piece consistent with Comparative Example 1 was produced usingNylon 6 resin in the same manner as the test pieces consistent with thepresent Examples except for molding the whole body into the same shapeas the test piece P by single injection molding.

The tensile strength of the test piece consistent with ComparativeExample 1 was 76.3 MPa with a standard deviation of 0.8 MPa.

Comparative Example 2

A test piece consistent with Comparative Example 2 was produced in thesame manner as the test pieces consistent with the present Examplesexcept for applying no joining auxiliary to a joining end surface 1 ofits primary molded part P1. Besides, as a material for this test piece,Nylon 6 resin was used.

The tensile strength of the test piece consistent with ComparativeExample 2 was 13.3 MPa with a standard deviation of 9.2 MPa.

Comparative Example 3

A test piece consistent with Comparative Example 3 was produced usingNylon 66 resin in the same manner as the test pieces consistent with thepresent Examples except for molding the whole body into the same shapeas the test piece P by single injection molding.

The tensile strength of the test piece consistent with ComparativeExample 3 was 78.8 MPa with a standard deviation of 1.8 MPa.

Comparative Example 4

A test piece consistent with Comparative Example 4 was produced in thesame manner as the test pieces consistent with the present Examplesexcept for applying no joining auxiliary to a joining end surface 1 ofits primary molded part P1. Besides, as a material for this test piece,Nylon 66 resin was used.

The tensile strength of the test piece consistent with ComparativeExample 4 was 6.1 MPa with a standard deviation of 1.5 MPa.

Comparative Example 5

A test piece consistent with Comparative Example 5 was produced usingNylon 12 resin in the same manner as the test pieces consistent with thepresent Examples except for molding the whole body into the same shapeas the test piece P by single injection molding.

The tensile strength of the test piece consistent with ComparativeExample 5 was 43.1 MPa with a standard deviation of 0.3 MPa.

Comparative Example 6

A test piece consistent with Comparative Example 6 was produced in thesame manner as the test pieces consistent with the present Examplesexcept for applying no joining auxiliary to a joining end surface 1 ofits primary molded part P1. Besides, as a material for this test piece,Nylon 12 resin was used.

The tensile strength of the test piece consistent with ComparativeExample 6 was 5.9 MPa with a standard deviation of 0.9 MPa.

Consideration of Test Results

It was shown that the test pieces consistent with Examples 1 to 34(using Nylon 6) have joining strengths bearing comparison with that ofthe test piece consistent with Comparative Example 1 produced by singleinjection molding.

Similarly, it was shown that the test pieces consistent with Examples 35to 68 (using Nylon 66) also have joining strengths bearing comparisonwith that of the test piece consistent with Comparative Example 3 formedby single injection molding.

Similarly, it was shown that the test pieces consistent with Examples 69to 71 (using Nylon 12) also have joining strengths bearing comparisonwith that of the test piece of Comparative Example 5 formed by singleinjection molding.

In addition, it was shown that the test pieces consistent with Examples1 to 34 have excellent joining strengths compared with the test piececonsistent with Comparative Example 2 in which joining was performedwithout using any joining auxiliary.

Similarly, it was shown that the test pieces consistent with Examples 35to 68 have excellent joining strengths compared with the test piececonsistent with Comparative Example 4 in which joining was performedwithout using any joining auxiliary.

Similarly, it was shown that the test pieces consistent with Examples 69to 71 have excellent joining strengths compared with the test piececonsistent with Comparative Example 6 in which joining was performedwithout using any joining auxiliary.

This is assumed to be brought about because, when the joiningauxiliaries consistent with the present Examples were applied to thejoining end surfaces 1, the polyamide resins on the joint end surfaces 1were activated by the reduction effect of the components (A) and theadditive molded parts P2 were injection welded to the activated joiningend surfaces 1, whereby both were strongly connected mainly by chemicalbonding to be integrated in the recrystallization process of the meltedpolyamide resins.

The present invention is never limited to the above-mentioned Examples,and various changes can be made without departing from the scope of thepresent invention. For example, although the above-mentioned Examplesdescribe polyamide resin integrally molded products manufactured bymeans of injection welding, the polyamide resin integrally moldedproducts can be also manufactured by means of ultrasonic welding,vibration welding or the like by mutually welding the joint sites of thepolyamide resin molded products by use of the joining auxiliaryaccording to the present invention.

1. A polyamide resin integrally molded product comprising: a polyamideresin molded product to a joint site of which a joining auxiliary isapplied; and a polyamide resin to form an additive molded product part,which is welded to the joint site of the polyamide resin molded productto be integrated, wherein the joining auxiliary contains:trihydroxybenzene and/or trihydroxybenzoic acid as a component (A); andan organic solvent which is capable of dissolving or dispersing thecomponent (A), as a component (B).
 2. A polyamide resin integrallymolded product comprising: a polyamide resin molded product; and anotherpolyamide resin molded product, to at least one joint site of thepolyamide resin molded products, a joining auxiliary being applied tomutually weld and integrate the joint sites, wherein the joiningauxiliary contains: trihydroxybenzene and/or trihydroxybenzoic acid as acomponent (A); and an organic solvent which is capable of dissolving ordispersing the component (A), as a component (B).
 3. The polyamide resinintegrally molded product according to claim 1 or 2, wherein thecomponent (A) further contains dihydroxybenzene and/or dihydroxybenzoicacid.
 4. The polyamide resin integrally molded product according toclaim 1, wherein a content of the component (A) is not less than 1 wt %and not more than 50 wt %, and a content of the component (B) is notless than 50 wt % and not more than 99 wt %.
 5. The polyamide resinintegrally molded product according to claim 1, wherein the component(B) is a mixed organic solvent obtained by mixing two or more sorts ofthe organic solvents.
 6. A method for manufacturing a polyamide resinintegrally molded product, comprising the steps of: applying a joiningauxiliary to a joint site of a polyamide resin molded product; andwelding a polyamide resin which is to form an additive molded productpart to the joint site of the polyamide resin molded product, whereinthe joining auxiliary contains: trihydroxybenzene and/ortrihydroxybenzoic acid as a component (A); and an organic solvent whichis capable of dissolving or dispersing the component (A), as a component(B).
 7. A method for manufacturing a polyamide resin integrally moldedproduct, comprising the steps of: applying a joining auxiliary to atleast one joint site of polyamide resin molded products; and welding thejoint sites mutually, wherein the joining auxiliary contains:trihydroxybenzene and/or trihydroxybenzoic acid as a component (A); andan organic solvent which is capable of dissolving or dispersing thecomponent (A), as a component (B).
 8. The method for manufacturing thepolyamide resin integrally molded product according to claim 6 or 7,wherein the component (A) further contains dihydroxybenzene and/ordihydroxybenzoic acid.
 9. The method for manufacturing the polyamideresin integrally molded product according to claim 6, wherein a contentof the component (A) is not less than 1 wt % and not more than 50 wt %,and a content of the component (B) is not less than 50 wt % and not morethan 99 wt %.
 10. The method for manufacturing the polyamide resinintegrally molded product according to claim 6, wherein the component(B) is a mixed organic solvent obtained by mixing two or more sorts ofthe organic solvents.
 11. A joining auxiliary for polyamide resincontaining: trihydroxybenzene and/or trihydroxybenzoic acid as acomponent (A); and an organic solvent which is capable of dissolving ordispersing the component (A), as a component (B).
 12. The joiningauxiliary for polyamide resin according to claim 11, wherein thecomponent (A) further contains dihydroxybenzene and/or dihydroxybenzoicacid.
 13. The joining auxiliary for polyamide resin according to claim11 or 12, wherein a content of the component (A) is not less than 1 wt %and not more than 50 wt %, and a content of the component (B) is notless than 50 wt % and not more than 99 wt %.
 14. The joining auxiliaryfor polyamide resin according to claim 11, wherein the component (B) isa mixed organic solvent obtained by mixing two or more sorts of theorganic solvents.